class Solution {
public:
    int peakIndexInMountainArray(vector<int>& arr) {
            int left=0;int right=arr.size()-1;
            int target=0;
            for(int i=0;i<arr.size();i++)target=max(target,arr[i]);
            while(left<right)
            {
                int mid=left+(right-left)/2;
                if(arr[mid]<arr[mid+1])left=mid+1;
                else if (arr[mid]>arr[mid+1])right=mid;
            }
            return right;
    }
};
